Photovoltaic energy is becoming an ever more significant source of electrical power. This is due in part to the growing concern over problems of pollution, safety and scarcity associated with conventional sources of power such as fossil fuels and nuclear energy; and also because of recent advances in technology which have made possible the manufacture of lightweight, large area, low cost photovoltaic devices based upon thin film semiconductor materials.
The power generated by a photovoltaic device is proportional to the illumination incident thereupon, and if relatively large amounts of power are to be generated, fairly large collection areas are required. The roof and upper story areas of building structures are well illuminated, and are generally not productively used. For some time now it has been known to place photovoltaic devices onto the upper portions of buildings, and U.S. Pat. Nos. 5,232,518 and 5,092,939 both disclose particularly configured roofing members having photovoltaic devices affixed thereto. As disclosed in both of these patents, photovoltaic devices are affixed to building panel members during their fabrication, and as is specifically disclosed in U.S. Pat. No. 5,092,939, the photovoltaic devices are laminated to sheet metal stock by a roller based lamination process, and this stock is subsequently bent into an appropriate shape to provide a batten and seam roofing panel.
While the roller based lamination process disclosed in the foregoing is of significant utility, it is not always practical to employ a lamination process of the type disclosed therein. Furthermore, it is often desirable to attach a photovoltaic device to a commercially available, preformed panel. For example, a particular building application may require use of a specific manufacturer's preformed architectural panel either because that panel has already been rated and approved by appropriate agencies, or because it has been specified by a consumer, or because a particular product is already in inventory. Therefore, there is a need for a preformed architectural panel of conventional, commercially accepted design, which further includes a photovoltaic generating element thereupon.
Preformed architectural panels typically include a number of structural features defined thereupon such as raised, bent or otherwise configured connector flanges, reinforcement ribs, interlocks or the like. In other instances, the preformed architectural panel may include a concave or convex central portion onto which a photovoltaic device is to be attached. The presence of such structural features makes the use of a pressure roll lamination process difficult, if not impossible, to implement on preformed panels. Therefore, it will be appreciated that there is also a need for a process whereby photovoltaic devices, particularly large area photovoltaic devices, may be laminated onto relatively large, preformed architectural panels. Often, it will be desirable that the lamination be carried out at a construction site, and in some particular instances, there is a need for a method for laminating photovoltaic devices onto architectural panels which are already affixed to a building structure. In some instances, photovoltaic generating devices may be simply affixed to panels by adhesive or the like; but in other instances, pressure and/or heat must be used to assure a tight bond.
Vacuum lamination processes have been employed in the prior art for the attachment of photovoltaic devices to supporting substrates. However, previous vacuum lamination processes have all required relatively large and complicated lamination systems. For example, U.S. Pat. No. 4,450,034 discloses a vacuum lamination system for use with relatively large work pieces. The system includes a large area framework made from metal I-beam members. It is relatively heavy and expensive, and is not readily adaptable for use at a construction site. Furthermore, the system cannot be employed to laminate photovoltaic devices to a portion of a standing building. Another lamination system is disclosed in U.S. Pat. No. 4,421,589. The system described therein is only capable of accommodating modest sized panels, and comprises a large, precise apparatus not amenable to on site use. Other vacuum lamination processes are shown in U.S. Pat. Nos. 4,382,833; 4,287,382; 4,210,462; 4,184,903 and 5,238,519 as well as in Japanese Patent 1,024,426.
All of the foregoing prior art systems require extensive hardware for supporting a substrate during a lamination process. In addition, the systems are not adaptable for laminating onto nonplanar substrates such as architectural panels having upstanding seams, interlocks and the like. Furthermore, none of the disclosed systems can be operated to laminate a photovoltaic device onto a curved substrate.
It will thus be understood that there is also a need for a lamination method which can be employed to affix photovoltaic devices to architectural building panels, including panels with nonplanar surfaces. The present invention provides for building panels of conventional design, having photovoltaic devices attached thereto, as well as a lamination method which can be advantageously used for their fabrication. The method of the present invention requires minimal hardware and actually uses a portion of the building panel as a part of the lamination system itself. The method of the present invention can be utilized in an on-site application and on standing building structures. These and other advantages of the present invention will be apparent from the drawings, discussion and description which follows.